Question

Calculate the volume of 1.00 M acetic acid solution and mass of sodium acetate needed to make 250 mL of a 0.450 M acetic acid/acetate buffer solution with a pH of 4.00. (The pKa is 4.74 for acetic acid).

Answer 1

I work these buffer problems with millimols instead of M.
You want 250 mL x 0.450M = 112.5 millimols of the buffer.
so equation 1 is base + acid = 112.5

Equation 2 comes from the HH equation.
pH = pKa + log (base)/(acid)
4.00 = 4.74 + log b/a
Solve for b/a and rearrange to
base = ?*a. This is equation 2.

Solve the two equations simultaneously for millimols base and acid, then convert mmols acid to mL of the 1.0 M and convert mmols base to g NaAc.

Answer 2

Dr bob can you please elaborate a little more I struggling to put it together